WIKIMEDIA, NIAIDFor all the myriad genome-editing tricks of the CRISPR/Cas9 system, slipping into cells by way of viral vector was previously not one of them. The gene for the large Cas9 enzyme—which originated from the Streptococcus pyogenes bacterium—maxed out the carrying capacity of vectors’ genomes. Researchers from the Broad Institute and MIT and their colleagues have now found that a smaller Cas9 from a different bacterium can do the job with ease. They described their modified approach in Nature today (April 1).
“The paper illustrates that there is more to the Cas9 world than the first characterized protein (nuclease), and that new avenues will open as the toolbox is expanded,” Rodolphe Barrangou of North Carolina State University who was not involved in the study wrote in an e-mail.
As part of a bacterial and archaeal immune response commonly referred to as CRISPR, the Cas9 enzyme cleaves a pre-specified sequence of DNA. Biologists have repurposed Cas9 to precisely rewrite genetic code and manipulate gene function in the lab.
The most commonly employed Cas9, measuring in at 4.2 kilobases (kb), comes from S. pyogenes. While it’s an efficient nuclease, the molecule’s length pushes the limit of how much genetic material an adeno-associated virus (AAV) vector can load up on, ...
